The present invention relates generally to steam attemperation. More specifically, the invention relates to attemperation of steam bypassed from a steam turbine during tripping of the steam turbine.
In combined cycle power plants, heated exhaust from a gas turbine may be sent to a heat recovery steam generation (HRSG) system for producing steam, which may be used in steam turbines. HRSG systems may produce steam at very high temperatures. In particular, HRSG systems may include superheaters and re-heaters, which superheat steam used by the steam turbines. During tripping of the steam turbines, the steam may bypass the steam turbine. In this scenario, the steam temperatures, if uncontrolled, may become even greater in that the steam may simply loop between the superheaters and re-heaters.
If the steam from the superheaters and re-heaters reaches high enough temperatures, the steam turbine, as well as other equipment downstream of the HRSG, may be adversely affected. For instance, high cyclic thermal stress in the steam piping and steam turbine may eventually lead to shortened life cycles. Conventional control systems have been devised to help monitor and control the temperature of steam within HRSG systems. However, these conventional control systems often involve using attemperation systems, which utilize water from dedicated water sources as the cooling medium. Using dedicated water sources and piping may lead to oversizing of water tanks and water pumping equipment, thereby leading to increased footprints of the equipment and overall HRSG system.